using System;

using System.Globalization;

using System.ComponentModel;

using System.Threading.Tasks;

using Microsoft.Extensions.Configuration;

​

​

public class Program

{

    public static void Main()

    { 

        // Simulate values being set in the environment

        Environment.SetEnvironmentVariable("SomeSettings__ApiUrl", "set-via-env");

        Environment.SetEnvironmentVariable("SomeSettings__Timeout", "10");

        Environment.SetEnvironmentVariable("SomeSettings__ApiKey", "arn:api:key:name");

        IConfiguration config = new ConfigurationBuilder()

            .AddEnvironmentVariables() // lookup values from Environment

            .Build();

        var settings = new SomeSettings();

        config.GetSection("SomeSettings").Bind(settings);

        // Main() can't be async, so this lets us use async/await in Handler()

        Handler(settings).Wait();

    }

    public static async Task Handler(SomeSettings settings)

    {

        Console.WriteLine($"ApiUrl: {settings.ApiUrl}");

        Console.WriteLine($"Timeout: {settings.Timeout}");

        var apiKey = await settings.ApiKey.Value;

        Console.WriteLine($"ApiKey: {apiKey}");

    }

}

​

// Simulated Strong-typed Config section

public class SomeSettings {

  public string ApiUrl { get; set; }

  public int Timeout { get; set; }

  public Secret ApiKey { get; set; }

}

​

// Class that manages access to a secret by key

[TypeConverter(typeof(SecretTypeConverter))]

public class Secret {

    public Task<string> Value { get; protected set; }

    public Secret( string key ) {

        Value = LookupSecretByKey(key);

    }

    protected Task<string> LookupSecretByKey(string key)

    {

        // this is where we'd trigger the SecretsManager async call

        return Task.FromResult($"secret-value[{key}]");

    }

}

​

// Handles allowing the IConfigurationSection's Bind() to convert a string into a Secret() 

public class SecretTypeConverter : TypeConverter

{

    public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)

    {

        return sourceType == typeof(string) || base.CanConvertFrom(context, sourceType);

    }

​

    public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)

    {

        var casted = value as string;

        return casted != null

            ? new Secret(casted)

            : base.ConvertFrom(context, culture, value);

    }

}